A291756 Compound filter: a(n) = P(A003557(n), A000010(n)), where P(n,k) is sequence A000027 used as a pairing function.

1, 1, 2, 5, 7, 2, 16, 25, 31, 7, 46, 12, 67, 16, 29, 113, 121, 31, 154, 38, 67, 46, 232, 59, 281, 67, 334, 80, 379, 29, 436, 481, 191, 121, 277, 142, 631, 154, 277, 175, 781, 67, 862, 212, 328, 232, 1036, 261, 1135, 281, 497, 302, 1327, 334, 781, 355, 631, 379, 1654, 138, 1771, 436, 706, 1985, 1129, 191, 2146, 530, 947, 277, 2416, 607, 2557, 631, 951, 668, 1771

Offset: 1

Author

Antti Karttunen, Sep 10 2017

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..16385

Crossrefs

Cf. A000010, A000027, A003557, A291757, A291764.

Programs

PARI

A000010(n) = eulerphi(n);
A003557(n) = n/factorback(factor(n)[, 1]); \\ This function from Charles R Greathouse IV, Nov 17 2014
A291756(n) = (1/2)*(2 + ((A003557(n)+A000010(n))^2) - A003557(n) - 3*A000010(n));

Formula

a(n) = (1/2)*(2 + ((A003557(n)+A000010(n))^2) - A003557(n) - 3*A000010(n)).